1. Field of the Invention
The present invention relates to a method, system, and program for merging log entries from multiple recovery log files.
2. Description of the Related Art
A database system is one in which data is stored, retrieved, and processed. Data records in a relational database management system (RDBMS) in a computer are maintained in tables, which are a collection of rows all having the same columns. Each column maintains information on a particular type of data for the data records which comprise the rows. Tables in the database are searched using, for example, a Structured Query Language (SQL), which specifies search operations or predicates to perform on columns of tables in the database to qualify rows in the database tables that satisfy the search conditions.
Whenever a business grows, the amount of data stored by the business also grows. Whenever the amount of data grows, so do the demands to the database systems that manage the data. Today, most of the business information is stored and processed in database systems, and the-demands to the database systems that handle this data are tremendous. Despite the fact that these database systems handle terabytes of data, end-users and applications have the same demands to the database systems as they had decades ago, when database systems did not handle as much data. End-users and applications demand high performance from database systems. For example, database systems are expected to provide short response times to user requests and are expected to be always available.
A non-distributed database system fails to meet these requirements. On the other hand, distributed database technology may be able to do so. Distributed database technology refers to a collection of logically related databases distributed over a computer network. Distributed database systems deal with the performance aspect of a database system. By using interconnected computer systems, it is possible to manage large databases of several terabytes and yet provide reasonable response times for complex database queries. DB2® Enterprise Extended Edition (DB2® EEE®) is a product available from International Business Systems, Inc. (IBM) for a distributed database management system. An enterprise is a business that utilizes computers. For further information, see IBM® DB2® Universal Database Enterprise—Extended Edition, “Quick Beginnings V7”, Document Number GC09-2963-00, 2000, which is incorporated by reference herein in its entirety.
Distributed database technology was derived in the late 1970s due to a need to integrate data from several data sources into one database system and to achieve improved processing performance. For example, for a large company that manages several terabytes of data, a single database system was not able to handle the large amount of data and provide good performance. A solution to this problem was to exploit the power of parallel computing. But parallelism can only be achieved in a database system if the amount of data is split into several parts and manipulated in parallel. From the need for parallelism, came the need for distribution.
Data replication is the process of copying data from a source database to one or more target databases. Data replication provides many advantages to an enterprise's database system and gives businesses a sophisticated means to improve their database system's availability. Data replication allows businesses to have their data available where the businesses want the data and when the businesses need the data, by maintaining identical copies of a data source in several locations. Data replication is not tied directly to database technology. For example, data replication can also be found in file replication tools.
Data replication becomes more and more important for enterprises today. For example, the performance and the availability of a database system may highly increase by using data replication. DB2® DataPropagator (DPROPR®) is a product available from International Business Machines, Inc. (IBM) for relational data replication. For further information, see IBM® DB2® Universal Database, “Replication Guide and Reference V7”, Document Number SC26-9920-00, 2000, which is incorporated by reference herein in its entirety.
There is a need in the art for combining distributed database technology and data replication for improved database systems.